* {
    margin: 0;
    padding: 0;
    list-style: none;
}

ul {
    width: 500px;
    height: 500px;
    position: relative;
    left: 50%;
    top: 80px;
    transform: translateX(-50%);
    border: 1px solid red;
}

li {
    /* position: absolute; */
    box-sizing: border-box;
    width: 50px;
    height: 50px;
    border: 1px solid blue;
    float: left;
    /* background-color: black; */
}



.white {
    background-color: white;
}

.red {
    background-color: red;
}

p {
    text-align: center;
}

button {
    width: 200px;
    height: 100px;
    line-height: 100px;
    background-color: red;
    color: white;
    font-size: 40px;
    font-weight: bold;
    position: absolute;
    left: 50%;
    bottom: 10px;
    transform: translateX(-50%);
}

.blue {
    background-color: blue;
}